{"id":4031,"date":"2026-11-01T06:26:12","date_gmt":"2026-11-01T06:26:12","guid":{"rendered":"https:\/\/www.farmersforum.ie\/trends\/the-tropics-remain-richest-in-birds-but-cities-erase-much-of-this-advantage\/"},"modified":"2026-11-01T06:26:14","modified_gmt":"2026-11-01T06:26:14","slug":"the-tropics-remain-richest-in-birds-but-cities-erase-much-of-this-advantage","status":"publish","type":"post","link":"https:\/\/www.farmersforum.ie\/trends\/the-tropics-remain-richest-in-birds-but-cities-erase-much-of-this-advantage\/","title":{"rendered":"The Tropics Remain Richest in Birds, but Cities Erase Much of This Advantage"},"content":{"rendered":"

Close to the equator, bird diversity reaches its peak, then declines toward the poles. A study from McGill University, published in August 2026 in PNAS, shows that urbanization strongly weakens this contrast. Tropical cities indeed lose a larger share of their biodiversity than those at high latitudes.<\/p>\n

<\/figure>\n

A McGill team leveraged eBird observations of more than 10,000 bird species across five continents<\/h2>\n

The study, titled \u00ab Urbanization weakens the global latitudinal diversity gradient in birds \u00bb, was published on 18 August 2026 in the Proceedings of the National Academy of Sciences<\/strong>. It is credited to Jory Griffith, Jennifer Sunday, and Anna Hargreaves<\/strong> from McGill\u2019s Department of Biology. The trio focused on the latitudinal diversity gradient<\/strong>, the pattern stating that species richness increases toward the tropics.<\/p>\n

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To measure it, the team relied on eBird<\/strong>, a platform where amateur ornithologists record their observations. The globe was divided into one-kilometer-square cells, and only those sufficiently surveyed were kept. Then, each cell was classified as urban, peri-urban, or natural depending on human density and the degree of landscape transformation by humans.<\/p>\n

In cities, the bird diversity gradient is three times weaker than in nearby natural habitats<\/h2>\n

The central result can be captured in a single figure: in urban areas, the gap in richness between the tropics and high latitudes is three times less pronounced<\/strong> than in natural spaces. In other words, cities tend to look more alike across latitudes. Moreover, this effect is observed in both hemispheres and in any season.<\/p>\n

On average, urbanization reduces local bird diversity by 32 %<\/strong>. However, this loss varies strongly with latitude. According to McGill\u2019s press release, it would reach about 42 % near the equator, versus only 12 % near polar regions\u2014figures that do not appear in the article\u2019s abstract.<\/p>\n

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Specialist species, more numerous in the tropics, disappear first from urbanized areas<\/h2>\n

The authors offer two complementary explanations. First, tropical communities harbor more specialist species<\/strong>, dependent on a specific habitat or resource. Yet these birds are precisely the ones most excluded from urban environments, in favor of generalist species able to exploit varied surroundings.<\/p>\n

Second, urbanization itself proves more intense at lower latitudes, where city growth is often rapid and poorly planned. Thus, the combination of more fragile birds and more abrupt habitat transformations amplifies the losses. According to Anna Hargreaves, this ecological pattern, stable for millennia, is now disrupted by human activity<\/strong>.<\/p>\n

Green-space-rich neighborhoods limit losses, a concrete path for tropical city planning<\/h2>\n

Researchers note, however, an encouraging nuance. The decline is less pronounced in peri-urban<\/strong> zones and in cities that preserve large vegetated areas. Consequently, urban planning could play a direct role in maintaining bird communities.<\/p>\n

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In parallel, these conclusions rely on volunteer observations, unevenly distributed across regions. That is why the team notes that they kept only cells where around 95 % of the species present appeared to be already recorded. The ongoing work will aim to identify urban species and their effects on pollination<\/strong> or predation.<\/p>\n","protected":false},"excerpt":{"rendered":"","protected":false},"author":1,"featured_media":4032,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[1041,802,1462,2637,2178,2636,2635],"class_list":["post-4031","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-news","tag-advantage","tag-birds","tag-cities","tag-erase","tag-remain","tag-richest","tag-tropics","generate-columns","tablet-grid-50","mobile-grid-100","grid-parent","grid-50"],"_links":{"self":[{"href":"https:\/\/www.farmersforum.ie\/trends\/wp-json\/wp\/v2\/posts\/4031","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.farmersforum.ie\/trends\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.farmersforum.ie\/trends\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.farmersforum.ie\/trends\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.farmersforum.ie\/trends\/wp-json\/wp\/v2\/comments?post=4031"}],"version-history":[{"count":1,"href":"https:\/\/www.farmersforum.ie\/trends\/wp-json\/wp\/v2\/posts\/4031\/revisions"}],"predecessor-version":[{"id":4033,"href":"https:\/\/www.farmersforum.ie\/trends\/wp-json\/wp\/v2\/posts\/4031\/revisions\/4033"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.farmersforum.ie\/trends\/wp-json\/wp\/v2\/media\/4032"}],"wp:attachment":[{"href":"https:\/\/www.farmersforum.ie\/trends\/wp-json\/wp\/v2\/media?parent=4031"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.farmersforum.ie\/trends\/wp-json\/wp\/v2\/categories?post=4031"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.farmersforum.ie\/trends\/wp-json\/wp\/v2\/tags?post=4031"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}